Determination of the optical interference of iron oxide nanoparticles in fluorometric cytotoxicity assays
Not provided.
36 MATERIALS SCIENCE↗
Engineering topics
Poerwoprajitno, Agus R.
Publications and source records attributed to Poerwoprajitno, Agus R..
Asymmetric nanoparticle oxidation observed in-situ by the evolution of diffraction contrast
Abstract The use of transmission electron microscopy (TEM) to observe real-time structural and compositional changes has proven to be a valuable tool for understanding the dynamic behavior of nanomaterials. However, identifying the nanoparticles of interest typically require an obvious change in position, size, or structure, as compositional changes may not be noticeable during the experiment. Oxidation or reduction can often result in subtle volume changes only, so elucidating mechanisms in real-time requires atomic-scale resolution or in-situ electron energy loss spectroscopy, which may not be widely accessible. Here, by monitoring the evolution of diffraction contrast, we can observe both structural and compositional changes in iron oxide nanoparticles, specifically the oxidation from a wüstite-magnetite (FeO@Fe 3 O 4 ) core – shell nanoparticle to single crystalline magnetite, Fe 3 O 4 nanoparticle. The in-situ TEM images reveal a distinctive light and dark contrast known as the ‘Ashby-Brown contrast’, which is a result of coherent strain across the core – shell interface. As the nanoparticles fully oxidize to Fe 3 O 4 , the diffraction contrast evolves and then disappears completely, which is then confirmed by modeling and simulation of TEM images. This represents a new, simplified approach to tracking the oxidation or reduction mechanisms of nanoparticles using in-situ TEM experiments.
36 MATERIALS SCIENCE↗
A single-Pt-atom-on-Ru-nanoparticle electrocatalyst for CO-resilient methanol oxidation
Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. In this report we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time.
36 MATERIALS SCIENCE↗
Facettierte verzweigte Nickel‐Nanopartikel mit variierbarer Verzweigungslänge für die hochaktive elektrokatalytische Oxidation von Biomasse
Abstract Die Kontrolle der Bildung von verzweigten Nanopartikeln mit hoher Homogenität ist eine der größten Herausforderungen bei der Herstellung von Nanokatalysatoren mit verbesserter Aktivität und Stabilität. Mithilfe eines Mechanismus unter Nutzung eines kubischen Kerns und hexagonaler Verzweigung zur Bildung hochgradig monodisperser verzweigter Nanopartikel wurde die Länge der Nickelverzweigungen variiert. Es hat sich gezeigt, dass die Verlängerung der Nickelzweige mit ihrer hohen Bedeckung der aktiven Facetten die Aktivität für die elektrokatalytische Oxidation von 5‐Hydroxymethylfurfural (HMF) als Beispiel für die Umwandlung von Biomasse verbessert.
Poerwoprajitno, Agus R.↗
Faceted Branched Nickel Nanoparticles with Tunable Branch Length for High‐Activity Electrocatalytic Oxidation of Biomass
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗